Thanks for writing in. I am a qualified and certified cardiologist and I read your mail with diligence.
Normal heart rate
varies between 60 to 90 therefore 85 falls within normal limit. Rate is supposed go up while doing any exertion like climbing stairs so that is also not abnormal. Do one thing, ask one of your parent to feel your pulse rate while you are asleep if it is between 50-75 that means there is nothing wrong with your heart rate or its rise. As far as skipping a beat is concerned. See, our heart beats for about 100,000 times a day (72x60x24) so 1% beats to be out of rhythm that include missed beats is perfectly normal occurrence. It is just that some people are more perceptive or more sensitive about it. If you still are not satisfied please ask your doctor, you will be thoroughly examined and if needed investigated accordingly. For present I do not recommend any treatment. Good Luck.
With Best Wishes
Dr Anil Grover